Delivery sheaths and medical electrical leads are often inserted into a patient's body by means of introducer systems. These introducer systems typically include an elongated sheath which is inserted into the blood vessel or other portion of the patient's body. A delivery sheath or lead may then be introduced through a lumen of the introducer. In those circumstances in which the lead or delivery sheath is to remain in the patient's body for a considerable period of time, it is desirable to be able to remove the introducer sheath without removing the lead or delivery sheath.
Another related procedure involves placing a lead at a target destination through a lumen of a delivery sheath. After the lead is in position, the delivery sheath must be removed from the body while leaving the lead undisturbed. If the lead is coupled to an isodiametric connector that is substantially the same size as the lead body, the delivery sheath can be removed from the body by pulling the delivery sheath over the connector. Many connectors, however, are larger than the lead body so that the delivery sheath cannot be withdrawn over the connector, and some other means of removal must be employed.
One commonly employed mechanism for removing an introducer sheath or a delivery sheath from around another device is to provide the sheath or delivery sheath with weakened zones so that it can be torn or split and thereby removed from around the encircled device. One introducer system employing this mechanism is illustrated in U.S. Pat. No. 5,409,469 issued to Scheaerf, incorporated herein by reference in its entirety.
Another commonly employed mechanism for removing a sheath or delivery sheath from around a delivery sheath or lead is to simply slit the sheath along its length as it is pulled proximally along the inner lead or delivery sheath and out of the patient's body. Various exemplary slitter designs are disclosed in U.S. Pat. No. 4,997,424 issued to Little, U.S. Pat. No. 6,159,198 issued to Gardeski, and U.S. Pat. No. 5,330,460 to Moss et al. These prior art designs include mechanisms that grasp or otherwise couple to a lead or catheter body. For example, the '424 patent to Little describes a slitter that includes an arcuate section having an inner peripheral wall that extends arcuately through an angle of at least about 180 degrees, and which is adapted to abut against a delivery sheath while an introducer tube is slit away from the catheter body.
Because prior art slitter tools are adapted to couple to the inner lead or catheter body while the encircling introducer or delivery sheath is being slit away, the dimensions of the slitter tool must be tailored for a particular lead or delivery sheath. For example, a slitting tool adapted to couple to a 4 French lead will not properly attach to a 2 French lead, and so on. As a result, pre-packaged lead, delivery sheath, or introducer kits must be provided with specific slitting tools sized for use with the devices in the kit, increasing manufacturing costs and inventory.
Another problem associated with the coupling mechanisms of prior art slitting tools involves difficulties with deployment. Prior art clamping mechanisms add unnecessary bulk and complexity to the slitter. Moreover, such tools may attach to a lead body in a manner that is not intuitive. As a result, the user may incorrectly couple the slitter to the lead body, and the outer surface of the lead may therefore be damaged during the slitting process.
Yet another difficulty with using prior art slitting tools has to do with lead dislodgement. The coupling mechanisms provided by prior art slitting tools could suddenly disengage from a lead during the slitting process. This may cause the lead body to abruptly move in a manner that dislodges the lead distal tip. As a result, the lead placement procedure must be repeated, resulting in additional trauma to the patient.
Another disadvantage with prior art slitting tools is that they are not designed ergonomically. For example, most prior art tools are adapted to be grasped by the user with the index finger and thumb in the general plane of the cutting blade. In this case, the reactionary force causing by the slitting process is resisted by squeezing the slitter between the index finger and the thumb, which does not provide good support. Moreover, many tools of this type require the palm of the hand to be generally facing in an upward direction, which tends to be unstable. Finally, grasping a slitting tool in this manner encourages the user to incorrectly push the slitter toward the delivery sheath rather than to pull the delivery sheath past the slitter in the correct manner of use. As a result, the slitting process is made much more difficult, and potential damage to the inner device may occur.
What is needed, therefore, is an improved slitting tool that addresses the forgoing problems.